Protective covers of one type or another for keeping rain, dust, snow and other debris from getting into or on surfaces that would either be damaged by such contaminants or at least have to be cleaned prior to use are commonplace. Examples of such uses are convertible tops for vehicles, swimming pool covers, boat covers, so-called "tonneau covers" for open-topped truck beds, etc. In each instance, the cover, if it be made of some sort of fabric as opposed to a rigid lid-forming element, must be detachably fastened in some way to a rigid frame which generally borders and encloses the area to be protected. While seldom elastic in the sense of a rubber sheet or the like, nevertheless, they are usually "stretchable" to some modest degree due primarily to the nature of the fabric and its expanse. For instance, a canvas or vinyl vehicle top can be draped over a frame, pulled taut and stretched the half inch or so necessary to have the particular fasteners used to attach it to the vehicle body mate with one another.
The conventional connectors used for detachably fastening such covers to a frame bordering the area to be protected are, of course, such things as hooks-and-eyes, lacing a rope back and forth between anchoring elements carried by the frame through a series of grommets in the cover, snap fasteners, so-called "hook-and-loop" (Velcro) fasteners and probably many others. One particular method for fastening vinyl convertible tops to the body of a vehicle employs a grooved rail mounted on the latter into which is folded a tongue-forming stiffener sewn within the hem of the cover which will be more fully described in connection with the detailed description of the related art which will follow presently.